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Wednesday, March 25, 2015

Herd Rank in Young Horses

Researchers in the Czech Republic recently studies the factors influencing dominance position in young horses, with emphasis on the role of the mother. Horses form stable linear dominance hierarchies based on agonistic interactions. Higher dominance positions are believed to be connected, in both genders, to better condition and higher reproductive success. Many variables play a role in forming the dominant-submissive relationships between horses; however, the maternal effect upon the dominance position of the offspring still remains unclear, as do the possible mechanisms of transference (“inheritance”).

Researchers hypothesized that the maternal dominance position, plus differences in suckling parameters or maternal style, may be responsible for later outcome of the offspring's dominance position, characterized by two variables: index of fighting success and rate of winning encounters. Researchers studied 8 groups of loose-housed lactating mares with foals and subsequently four groups of the same foals at 3 years of age.

Researchers found that the impact of age on the dominance position of the young horses and residence in the group impacted dominance position, not the maternal dominance position. Older foals reached higher dominance positions, independent of the dominance position, age, or experience of the mother. Researchers did not find support for direct inheritance of maternal rank on foal dominance position.

However, foals born to the same mare in two consecutive seasons tended to have the same dominance position they obtained at three years of age. This suggests an important constant effect of the mother on the social success of her progeny. However, researchers did not find a significant effect of any of the tested variables describing maternal characteristics or maternal care.

Dominance position depended significantly on the foal's age at observation, and the residence in the herd formed via sequential introducing of later-weaned groups of foals. The most dominant horses were mainly recruited from the first-weaned group of the season, and thus were also the oldest individuals in the herd. Further research is needed to discover the role of foal personality and mare style, and their links to possible dominance behaviors in a herd.

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Summarized by Krishona Martinson, PhD, University of Minnesota




Aged Horse Nutrition

Figure 1.  Aged horse.In species other than horses, such as humans, rats, and dogs, altered nutritional requirements associated with aging include a decrease in energy requirement. However, there is little published work comparing digestibility in healthy adult versus healthy aged horses. Researchers at Michigan State University hypothesized that there would be no differences in macronutrient digestibility between eight adult (5 to 12 years) and nine aged (19 to 28 years) horses fed three diets.    

Seventeen stock-type mares were randomly assigned for a 5-week period to one of three diets: only, hay plus a starch- and sugar-rich concentrate, or hay plus a fat- and fiber-rich concentrate. Each diet period comprised 3 weeks of outdoor group drylot feeding, 2 weeks of indoor stalled individual feeding, followed by a 72-hour digestibility trial including total urine and fecal collection. All horses were clinically healthy for the duration of the experiment. Feed, fecal, and/or urine samples were analyzed to determine dry matter, crude protein, fat, energy, calcium, phosphorus, apparent retention and apparent digestibility. Neutral detergent fiber digestibility was also determined.

Mean body weight was lower in aged than in adult horses (1,003 pounds vs. 1,102 pounds), but body condition score (BCS) did not differ between groups (aged horses: 4.8 BCS and adult horses: 5.1 BCS). No age differences in digestibility, apparent digestibility, or apparent retention were seen for any of the variables measured.

 Based on the results of this study, total tract macronutrient digestibility appears to be similar between healthy adult and aged horses. Data from this study support the hypothesis that older horses in good health and body condition do not automatically require changes to their core diet. However, owners should monitor changes in body condition and muscle mass as horses age. It is also important to note that the nutrient digestibilities of diseased aged horses and those with dental disorders may differ. For more information, click here.  

Summarized by: Krishona Martinson, PhD, University of Minnesota




Monday, June 2, 2014

Stress During Transport

Acupuncture points combined with medication appear to reduce stress in horses during road transport.

Acupuncture has been shown to have the beneficial effect of reducing stress responses in animals and humans. Pharmacopuncture is the injection of subclinical doses of drugs into acupoints to give therapeutic results without side effects. This study, conducted by researchers in Brazil, compared the effects of injecting the usual dose of acepromazine (ACP; 0.1 mg/kg, intramuscularly [I.M.]) with those of pharmacopuncture (1/10 ACP dose at the governing vessel 1 [GV 1] acupoint) on the stress responses of healthy horses undergoing road transport for 2.5 hours.

Four different treatments were applied immediately before loading, with 8 animals/treatment: injection of saline or ACP (0.1 mg/kg, I.M.) at the base of the neck; and injection of saline or 1/10 ACP (0.01 mg/kg) at the GV 1 acupoint.

The road transport increased heart rate (HR), respiratory rate, body temperature, and serum cortisol of the untreated horses (injected with saline at the base of the neck). Pharmacopuncture at GV 1 reduced the average HR and transport-induced increase in HR at unloading, without changing the other variables. On the other hand, ACP (0.1 mg/kg) produced significant sedation and reduced the transport-induced increase in respiratory rate but without preventing the stress-induced increase of cortisol.

Other acupuncture points and drugs should be tested to verify the beneficial effect of this therapy to reduce stress in horses during road transport.

Summarized by: Krishona Martinson, PhD, University of Minnesota

Monday, January 13, 2014

Bandaging, Wound Healing and Proud Flesh Formation

Bandaging limb wounds resulted in the formation of proud flesh. However, if the proud flesh was removed, bandaging (or not bandaging) had no effect on total time to healing.

Many horse owners fear limb injuries, not only because of potential lameness issues, but because of the intense care that usually accompanies them. Recently, two studies investigated the use of different ointments and/or bandaging strategies in wound healing and granulation tissue (i.e. proud flesh) formation in limbs.

Researchers in Virginia set out to determine whether povidone iodine ointment or two forms of silver sulfadiazine applied topically to wounds on horse limbs affected the rate healing and the influence of bandaging on proud flesh formation. Six healthy adult horses were used. Six standardized skin wounds per horse were distributed between the dorsomedial surfaces of the metacarpi and metatarsi. One of the following 6 treatments was applied to each wound: 1% silver sulfadiazine cream with bandage, 1% silver sulfadiazine slow-release matrix with bandage, 1% silver sulfadiazine slow-release matrix without bandage, povidone-iodine ointment with bandage, untreated control with bandage, and untreated control without bandage. Wound area, proud flesh area, and perimeter were measured using digital images, and proud flesh was removed when present. Days until healing, rate of healing , rate of contraction, and epithelialization were compared among wound treatment groups.

Healing parameters did not differ among any of the wound treatment groups. All bandaged wounds produced proud flesh tissue, which was surgically removed; none of the un-bandaged wounds produced proud flesh tissue. When the proud flesh tissue was removed, rates of healing were not different among wound treatment groups, whether bandaged or un-bandaged.

In a separate study, researchers from Australia came to a similar conclusion. Their objective was to evaluate the effect of a non-occlusive dressing incorporated in a 3-layer bandage on limb would healing. Seventeen horses were bandaged with a non-occlusive dressing covered by gauze-coated cotton wool that was compressed with adhesive tape, while 16 horses were left un-bandaged. Standardised wounds were made on the skin overlying the dorsomedial aspect of the mid-metacarpus. Wounds were photographed weekly for nine weeks and the images were analyzed electronically.
There were significant effects associated with bandaging. In bandaged wounds, proud flesh tissue required regular trimming, but not in un-bandaged wounds. There was no difference between groups in the total days to healing or the overall rate of healing. If excessive granulation tissue was excised regularly, bandaging had no effect on total time to healing.

Both studies concluded that bandaging limb wounds resulted in the formation of proud flesh. However, if the proud flesh was removed, bandaging (or not bandaging) had no effect on total time to healing.

Summarized by: Krishona Martinson, PhD, Univ. of Minn.

Monday, November 25, 2013

Stress Response of Young Horses to Changes in Housing

Separating young horses from their group and stalling them in individual boxstalls is stressful.

For initial training, horses are often transferred from group housing to individual boxstalls, which is a potential stressor.

In a study conducted in Austria, salivary cortisol concentrations (an indicator of stress), locomotion activity, and heart rate were analyzed in eight 3-year old mares. Mares were transferred abruptly from group paddock housing to individual boxstalls without paddock access. Data were collected for 4 days while mares were in group housing and for 5 days immediately after the change in housing in individual boxstalls.

Once in boxstalls, mares underwent routine equestrian training for young horses. While in group housing, cortisol concentrations showed a diurnal rhythm with values approximately 0.6 ng/ml in the morning and a decrease throughout the day. When horses were moved to boxstalls, cortisol concentrations increased to 1.8 ng/ml within 30 minutes and did not return to baseline values for 6 hours. On the days following the housing change to boxstalls, a cortisol diurnal rhythm was re-established but at a higher level compared to the level found in group housing. Locomotion activity was higher when mares had access to a paddock than when kept in individual boxstalls and heart rate increased for approximately 60 minutes when mares were separated from their group.

This study confirms what was previously thought; separating young horses from their group and stalling them in individual boxstalls is perceived as stressful.

Friday, November 15, 2013

The effect of different feed delivery methods on time to consume feed in horses

Using obstacles can increase time to consume feed when feeding adult horses.

Management techniques that reduce the insulin response to feeding in horses have application in preventing insulin resistance and potential associations with diseases like laminitis. Eight mature idle horses with a body condition score between 5 and 6.5 and with no previous indication of insulin resistance were fed a meal of concentrate under 4 feed delivery treatments by researchers at North Carolina State University.

Treatments were all based on a bucket of equal dimensions. The treatments included a control and 3 treatments hypothesized to increase time to consume feed: mobile obstacles (BALL) above the feed, stationary obstacles below the feed in the form of a waffle insert (WAFFEL), and feed with water added (water).

Jugular venous blood samples were taken at feed delivery, every 10 minutes for the first hour, and then every 30 minutes until 300 minutes after feed delivery. The time to consume feed was different across treatment and was greater buckets with the BALL and WAFFEL obstacles when compared with the control and water added feed.

Glucose and insulin concentrations increased after feeding and tended to differ among treatments. Peak insulin and glucose concentrations were affected by treatment as were the time to peak insulin and the area under the curve of insulin. Therefore, feed delivery methods that include obstacles effectively increase time to consume feed and attenuate postprandial glucose and insulin concentrations.

A second experiment was designed to determine if the time to consume feed changes associated with BALL and WAFFEL obstacles in experiment 1 remain effective over a 4 day period. Four horses with no recent or regular history of consuming concentrates were fed concentrate meals for 4 consecutive days using the same treatments described in experiment 1. Horses were subject to a 4 day adaptation period and were randomly assigned to 4 day treatment periods using the 4 previously described treatments.

During adaptation, time to consume feed decreased over time. After adaptation, WAFFLE had greater time to consume feed when compared with the control and feed with water added, whereas feed with water added had the lowest time to consume feed overall.

Using obstacles to increase time to consume feed on a daily basis may be an effective method to reduce postprandial glucose and insulin concentrations, thereby decreasing the risk of insulin resistance development in horses.

Seasonal changes of total body water and water intake in Shetland ponies

Water supply during the cold seasons might be more critical than under summer conditions.

Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity.

A recent study conducted by scientists in Germany was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water and total water intake of 10 adult Shetland pony mares were estimated at monthly intervals for 14 months by using the deuterium dilution technique. During the last 4 months, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls.

The total body water in kg was closely related to body mass explaining 86% of the variation. In contrast to total body water in kg, total body water (percentage) remained relatively stable across all measurements. The total water intake showed an increase in summer and a decrease in winter. However, total water intake measured at ambient temperatures less than 0°C did not follow the same trend as total water intake at greater than 0°C. Therefore, removing total water intake values measured at ambient temperatures less than 0°C from the analysis resulted in high correlations with locomotor activity, ambient temperature, and resting heart rate.

Feed restriction had no effect on total water intake and total body water. The total body water content was unaffected by season and physical activity. The comparison of total water intake with published data on drinking water intake revealed that ponies had 1.7 to 5.1 times greater total water intakes when other sources of water such as feed and metabolic water were included. The total water intake was highly influenced by environmental conditions and metabolic rate.

Contrary to expectation, water supply during the cold seasons might be more critical than under summer conditions when water content of grass is high to allow for the compensation of limited availability of drinking water.
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